Sheath/core composite yarns

ABSTRACT

A BULKY TENSION-STABLE YARN HAVING STRETCH BROKEN FIBRES AS THE CORE AND CRIMPED STAPLE FIBRES AS SHEATH IS OBTAINED BY BLENDING SILVERS OF THE SAID FIBRES AND DRAFTING AND SPINNING ON A WORSTED SYSTEM.

United States Patent O 3,568,428 SHEATH/ CORE COMPOSITE YARNS Richard Stentiford, Pontypool, and Alan Roebuck, Harrogate, England, assignors to Imperial Chemical Industries Limited, London, England No Drawing. Filed Feb. 6, 1969, Ser. No. 797,224 Claims priority, application Great Britain, Feb. 15, 1968,

7,461/68 Int. Cl. D02g 3/00, 3/02, 3/36 U.S. Cl. 57--140 6 Claims ABSTRACT OF THE DISCLOSURE A bulky tension-stable yarn having stretch broken fibres as the core and crimped staple fibres as sheath is obtained by blending slivers of the said fibres and drafting and spinning on a worsted system.

The present invention relates to bulky sheath/ core composite yarns.

We have found that an especially useful and novel tension-stable bulky sheath/core yarn may be formed of stretch broken fibres, preferably uncrimped, forming a core surrounded by a sheath of crimped staple fibres.

Accordingly therefore, the present invention provides a bulked tension-stable core yarn comprising stretchbroken synthetic fibres located substantially centrally of the yarn to form a core portion and crimped staple fibres substantially surrounding the said stretch-broken synthetic fibres to form a sheath portion, the yarn having an extension of not more than when measured by the method as hereinafter defined.

The stretch-broken fibres may be formed from a tow of polyamide filaments, for example polyhexamethylene adipamide filaments, or other synthetic filaments and is preferably free of crimp, although some crimp may be imparted to the tow to assist in processing.

Any natural or synthetic fibre may be employed as the staple fibre sheath component, conveniently this may be formed from a crimped tow of polyamide by conventional crush cutting equipment, for example on a Pacific converter. The tow will normally be crimped in known stuffer box equipment.

A bulky tension stable yarn is a textile spun yarn which has a high resistance to extension at relatively low loads of the order of 0.025 g./den. A method of assessing this is to subject a 4 fold 8s worsted count spun yarn to a load of 100 g. Under such conditions we have found that the yarns of our invention have an extension of less than 10%.

The yarn of the present invention may be obtained by first blending slivers of stretch-broken synthetic fibres and staple fibres together to form a blended sliver and then drafting and spinning in a conventional worsted processing system. During the latter process the relatively uncrimped stretch-broken fibres tend to migrate to the centre of the yarn to form a core. Additional migration also may take place when the yarn is secured and dyed as a result of slight shrinkage differences which may exist between the components; yarn bulk is also increased during scouring and dyeing.

According to a further aspect therefore, the present invention provides a process for the manufacture of a bulked tension-stable core yarn as defined above wherein slivers of stretch-broken synthetic fibres and crimped staple fibres are blended together and the blend drafted and spun into a yarn which is subsequently scoured and dyed.

The following examples illustrate the present invention. In the examples the components were obtained as follows:

STRETCH-BROKEN COMPONENT A 300,000 denier unset tow having a crimp of 10 c.p.i. (crimps per inch) and an extension at break of 45% formed from 6 d.p.f. (denier per filament) polyhexamethylene adipamide filaments is subjected to stretch breaking on a Turbo-Stapler machine. The heat stretch zone is maintained at 350-400 F. and the total machine draft at 4.6. The tow is subjected to re-breaking after stretch-breaking and the resultant sliver has a fibre length of 2-8".

STAPLE FIBRE COMPONENT A 1,800,000 denier tow having a crimp of 15 c.p.i. and an extension at break of 50% is formed from 10 d.p.f. polyhexamethylene adipamide fibres and cut to 6" staple fibres in a Pacific-Converter. The tow is assembled from eighteen 100,000 denier tows and is steam set at 25 p.s.i.g. in a Sanderson steam cabinet for 7 minutes.

Example 1 Example 2 A sheath/ core yarn was produced by procedure of Example 1 except that the ratio of staple fibre to stretchibroken fibres Was 40% 60%. The spun yarn had an extension of 8.0%.

Fabrics knitted from the sheath/core yarns of the above examples showed properties of good recovery from deformation, a high area/weight ratio being comparable to that of wool and a resilient handle.

The fabrics obtained from the above example were assessed to have satisfactory handle after six hand washings or a machine washing. By satisfactory handle is meant that the fabrics did not show an undesirable increase in boardiness.

Examples 3 and 4 (comparative) Yarns were prepared by the procedure of Example 1 except that the amount of the stretch-broken component was reduced. The details of the yarns, their extension properties and the results of washing trials on fabrics knitted therefrom are shown in Table 1.

Examples 5 and 6 Yarns were again prepared according to the procedure detailed in Example 1 except that the stretch-broken component was formed from a 10 denier per filament polyhexamethylene adipamide tow, and the tow had an extension at break of 54%. Details of the yarn and its properties are given in Table 2.

What we claim is:

1. A bulked tension-stable core yarn comprising stretch-broken synthetic fibres located substantially centrally of the yarn to form a core portion and crimped staple fibres substantially surrounding the said stretchbroken synthetic fibres to form a sheath portion, the yarn having an extension of not more than 10% when measured by the method as hereinbefore defined.

2. A yarn according to claim 1 consisting wholly of fibres of polyhexamethylene adipamide.

3. A yarn according to claim 2 wherein the crimped staple fibres are 10 denier P r filament, have 15 crimps per inch and an extension at break of 50%, the stretch broken fibres are 6 denier per filament and comprise at least 40% of the yarn.

4. A yarn according to claim 2 wherein the crimped staple fibres are 10 denier per filament, have 15 crimps per inch and an extension at break of 50% and the stretch-broken fibres are 10 denier per filament and comprise at least 30% of the yarn.

5. A process for the manufacture of a bulked tensionstable core yarn comprising stretch-broken synthetic fibres located substantially centrally of the yarn to form a core portion and crimped staple fibres substantially surrounding the said stretch-broken synthetic fibres to form a sheath portion, the yarn having an extension of not more than 10% when measured by the method as hereinbefore defined wherein slivers of stretch-broken synthetic fibres and crimped staple fibres are blended together and the blend drafted and spun into a yarn which is subsequently scoured and dyed, the stretch-broken fibres being formed from a 300,000 denier 6 denier per filament polyhexamethylene adipamide tow at a breaking extension of 45% and a temperature of 400 F.

6. A process according to claim 5 wherein the crimped staple fibres are formed from 18 X 100,000 denier polyhexamethylene adipamide tows which are crimped steam set at 25 p.s.i.g. and cut to 6" staple fibres.

References Cited UNITED STATES PATENTS 2,810,281 l/l9'57 Appleton et a1. 5714OUX 3,077,006 2/1963 Ibrahim 57140UX 3,157,021 11/1964 Kitson et al. 57l40 3,137,991 6/1964 Fairley 57l40 3,161,011 12/1964 Humphreys 57-140 3,188,790 6/1965 Hebeler 57-140 3,255,580 6/1966 Garner et al. 57140 3,435,608 4/1969 Stanley 57-157 30 DONALD E. WATKINS, Primary Examiner US. Cl. X.'R. 57157 

